Captain's Mast was a non-judiciary court for minor violations which were held aboard Federation starships in the 23rd century, and was typically presided over by the ship's commanding officer. Amongst the punishments that could be handed down should an accused party be found guilty, was the assignment of extra duty shifts.
Admiral James T. Kirk presided over Captain's Mast aboard the USS Enterprise in the 2270s, where it was typically held in the ship's rec room in order to accommodate witnesses. During one Captain's Mast in 2277, Kirk presided over several cases including: an electrician first class who was accused of stealing special food off of a yeoman suffering from Rigellian bone-stress; a case of two specialist first classes who had failed to respond quickly enough to alerts; a sexual harrassment case against a female nutritionist and a petty officer who was accused of rigging the computer games so that she won money. (TOS - Star Trek II Short Stories short story: "The Blaze of Glory")